This invention is related to ball valve seat assemblies which have an annular seat ring member mounted in an annular groove around the flow passageway in a ball valve. Further, this invention is related to ball valve seat assemblies which employ a metallic seat ring member that carries an annular non-metallic seal member on one side thereof to contact the valve member.
In the prior art several general types of seat constructions are known which utilize a metal seat ring member to mount a non-metallic seal member. In the simplest of these constructions a cross-sectionally rectangular non-metallic seal ring is simply pressed into a cross-sectionally rectangular groove in the face of a seat ring member and retained in place due to compression of the non-metallic seal member. This construction has several major disadvantages, one of which is the difficulty in sizing the seal member and the grooves so the proper interference is provided. Another disadvantage is that this type of seal construction will sometimes blow out when the valve is opened or closed during a high velocity flow rate condition due to the seal member slipping on the sides of the groove.
Another construction for holding a non-metallic seal member in a metallic annular seat ring is to sandwich the seal member between two separate parts of a seat ring as shown in U.S. Pat. No. 3,416,558 issued Dec. 17, 1968 to M. T. Works. This construction provides for holding of the non-metallic seal member, however, it is expensive and difficult to manufacture as well as complicating the structure by requiring welding of the seat ring to secure the separate members.
Another seat construction utilizes an annular groove in the seat member with a wall of uniform thickness on one side of the groove being deformed by spinning to a position which overlies the side and a face end portion of the non-metallic seal member, thus holding it in place. This construction is shown in U.S. Pat. No. 3,827,673 issued Aug. 6, 1974 to R. C. Houlgrave et al. Another seat construction which apparently uses a heated non-metallic seal member that is pressed into a preformed groove in the seal member as shown in U.S. Pat. No. 3,729,015 issued Apr. 24, 1973 to J. P. Oliver. While this construction may serve to secure the non-metallic seal member, it utilizes a grooved construction which is extremely difficult to machine due to its intricate shape. Assembly of this seat is believed to require the heating and compression of the non-metallic material to force it into the groove.